This invention relates to a method and apparatus for tufting accent yarns in a patterned pile fabric, and more particularly to a method and apparatus for tufting clearly defined accent yarns in patterned pile fabrics.
Heretofore, in the formation of accent yarns in a tufted pile fabric, the accent yarn, usually of a different color from the surrounding field of pile fabric, forms periodic high pile contrasting with low pile in the same row of stitching. Sometimes the high pile accent tufts contrast with low pile in rows extending transversely of the accent yarn. However, the high pile accent tufts are of the same height as the surrounding field of high pile. Moreover, in attempting to form high pile accent loops in a single row of stitching, because of the inertia in the yarn feed rolls and the clutch mechanisms, the transition between the low and the high pile loops is usually gradual, thereby precluding any sharp or well-defined distinction between the high pile accent tufts and the surrounding field of the pile fabric. In normal situations where the high pile accent loop is formed conventionally, there is usually a cluster of high pile loops, in which the middle accent pile loop is higher than the flanking high pile loops, because of the gradual transition between the low loops and the high loops in the same row of accent yarn stitching.
It is known in the art to operate a yarn feed roll at a speed which would pull out all the pile and produce only a back stitch which would float across the back of the base fabric.
It is also known in the art to tuft pile fabric having three different pile heights, such as disclosed in the prior R. T. Card U.S. Pat. No. 3,075,482, issued Jan. 29, 1963.
It is also known in the mechanical arts to use a clutch brake arrangement which selectively drives a shaft when the clutch is energized and alternately to stop the shaft when the brake portion is energized.
Prior U.S. Pat. No. 4,864,946 issued to the applicant on Sept. 12, 1989, and owned by the common Assignee of this application, discloses a "Yarn Feed Split Roll Apparatus For Tufting Machine" in which a plurality of drive shafts are provided for being driven at selectively different speeds in order to selectively drive various sets of yarn feed rolls at either a high speed or a low speed in accordance with a predetermined pattern control mechanism, in order to produce tufted pile fabrics of two levels, namely, high pile and low pile.